Maths · Calculation of standard deviation, variance and mean deviation for grouped and ungrouped data

The mean deviation of the data from the mean is

The mean deviation of the data \( \mathbf{2}, \mathbf{9}, \mathbf{9}, \mathbf{3}, \mathbf{6}, \mathbf{9}, \mathbf{4} \) from the mean is

  • A. 2.23
  • B. 2.57
  • C. 3.23
  • D. 3.57

Step-by-step solution

Mean = (2+9+9+3+6+9+4)/7 = 42/7 = 6. Deviations from mean: |2-6|=4, |9-6|=3, |9-6|=3, |3-6|=3, |6-6|=0, |9-6|=3, |4-6|=2. Sum of deviations = 4+3+3+3+0+3+2 = 18. Mean deviation = 18/7 ≈ 2.57.
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